The goal of the research is to examine the mechanisms by which the central nervous system mediates various aspects of sociosexual behavior in mammals. There is an emphasis on the hormonal control or modulation of these mechanisms. A region of particular interest is the medial preoptic-anterior hypothalamic area of the basal forebrain because this area appears to be the single most important area in the mediation of male sexual behavior and some other sexually dimorphic behavioral patterns of males. A concept that will be explored is whether this area of the brain is the primary androgen target tissue for the maintenance and activation of male sexual behavior by testosterone. Another aspect of the proposed research is to examine the role of this brain area in female behavior. The development of neuropsychological concepts that may apply to several mammalian species, including the human species, is of special concern. The comparative approach will be utilized, but the species used in any particular experiment is that which is felt to be the most appropriate for the problem or concept being investigated.